7-8
Intel
®
Pentium
®
III Processor with 512KB L2 Cache Dual Processor Platform Design Guide
7.9.1
Power On Sequence
The power on sequence for the Intel
®
Pentium
®
III Processor with 512KB L2 Cache has changed as
compared to AGTL+ only processors. The Intel
®
Pentium
®
III Processor with 512KB L2 Cache now
receives VTT_PWRGD as part of the sequence to indicate that the voltage regulator can latch the
processor’s operating voltage and begin to drive Vcc
CORE
. Please refer to the Intel
®
Pentium
®
III
Processor with 512KB L2 Cache Datasheet for more information on the required power up sequence.
7.9.2
Signalling Changes
On the Intel
®
Pentium
®
III Processor with 512KB L2 Cache, the VID and BSEL signals are true open
drain CMOS outputs and are no longer shorts or opens to VSS. Because of this, these signals now need
to be pulled-up to 3.3V through 1K
Ω
resistors.
7.9.3
Legacy Clock Driver Support
In legacy systems being converted to Intel
®
Pentium
®
III Processor with 512KB L2 Cache based
systems and in single-ended clocking systems, the clock driver may not support the new VTT-PWRGD
signal. In this case, it is necessary to modify the standard power sequencing circuit mentioned in the
Intel
®
Pentium
®
III Processor with 512KB L2 Cache Datasheet.
Figure 7-5
shows a summary of
modifications needed.
Figure 7-5. SE Clocking Implementation
VRM1
VRM2
CPU2
CPU1
CLK
BSEL1
BSEL0
BCLK
BCLK
VTT_PWRGD
VID[3:0],25mV
VID[3:0],25mV
VTT
1k
Ω
1k
Ω
VTT_PWRGD
VTT
1k
Ω
1k
Ω
3.3v
3.3V
Содержание Pentium III
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